1. Field of the Invention
The present invention relates a method and apparatus that remains onboard a tractor and semi trailer vehicle for readily instructing axle alignment to an operator.
2. Description of Prior Art
Since the beginning of the tractor and semi trailer vehicle, alignment technicians have relied on various techniques for checking and correcting axle alignment. These techniques include using devices such as measuring tapes, strings, lasers, tram bars, devices attached to the wheels, devices attached to the kingpin, and the latest to this era, computer projecting imagery with printout capabilities. However, all of these devices depend on an operator to setup and measure the vehicle's alignment in a static position and often with the wheels elevated in order to compensate for tire and wheel run-out before anyone could diagnose axle alignment.
Fleet vehicles such as a semi trailer should seriously be maintained for proper axle alignment, especially those with tandem axles, since these vehicles are dangerously transporting the heaviest loads which can be detrimental to axle alignment through curbing and poor road conditions.
Incorrect axle alignment occurs when an axle becomes deviated from the original drive path of the vehicle. Deviation of a single rear axle will cause the tires to automatically roll to one side of the vehicle's centerline. The vehicle then appears to be rolling awry to the normal direction of travel. This alignment causes reduced fuel mileage, increased rolling resistance and driver fatigue from constant correction of the vehicle due to poor handling characteristics associated with this type of alignment.
With tandem axle combinations, both axles must be parallel to one another to minimize scrubbing between the tires and the roads surface. If one axle becomes deviated from the other, a tandem scrub angle occurs. This is the angle formed by two thrust lines of a tandem axle vehicle. The term (thrust line) used in this document represents the direction that the axle points compared to the vehicle's centerline (shown in FIG. 3).
Upon deviation of a tandem axle the driver is forced to turn the front steer axle to offset the push of the tandem axles in order to keep the vehicle moving straight ahead. This causes a constant scrubbing between each tire on the vehicle and the roads surface. The results are reduced fuel mileage, driver fatigue from poor handling of the vehicle, excessive premature tire wear, and an increase in tire temperature. Tire temperature can be a contributing factor for the rapid disintegration of the tire's tread which is hazardous and often seen laying along the roadway.
Most axle alignment problems are unseen to the eye. Because of this fact it possible to overlook alignment problems that might exist with the axles for a long period of time, since many of these problems will take several hundred to even thousands of miles to manifest themselves and become a contention to the driver.
There are several types of axle alignment devices found in prior art which include devices that are attached and removed, drive-on alignment devices, and an onboard axle misalignment monitor.
Attach and remove devices belong to U.S. Pat. No. 2,479,723 by Brown (1949), U.S. Pat. No. 2,845,718 by Keymer (1958), U.S. Pat. No. 3,279,084 by Hinden (1966), U.S. Pat. No. 3,325,905 by Hurst (1967), U.S. Pat. No. 3,566,476 by McWhorter (1971), U.S. Pat. No. 3,686,770 by Davis (1972), U.S. Pat. No. 3,962,796 by Johnston (1976), U.S. Pat. No. 4,347,668 by Johnston (1982), U.S. Pat. No. 4,800,651 by Hanlon (1989), U.S. Pat. No. 4,942,667 by Fournier (1990), U.S. Pat. No. 5,157,838 by Sims (1990), U.S. Pat. No. 6,021,576 by Campbell (2000), U.S. Pat. No. 6,082,011 by Phillips (2000), U.S. Pat. No. 6,233,837 by Hagelthorn (2001), U.S. Pat. No. 6,397,448 by Cobb (2002), U.S. Pat. No. 6,435,044 by Adolph (2002), U.S. Pat. No. 6,886,266 by Kidd (2005), U.S. pre-grant 20040163265 by Helms, and pre-grant 20050005461 by Rohrig. However, setup of the above mentioned alignment devices requires time and precision. Obtaining the same alignment results are often difficult when used by different technicians.
Drive-on alignment devices belong to U.S. Pat. No. 3,137,076 by Hurst (1964), U.S. Pat. No. 4,005,899 by Dean (1997), and U.S. Pat. No. 5,386,639 by Colarelli (1995). These devices are large and not easily transported, which eliminates the benefit of field alignment.
U.S. Pat. No. 6,405,109 B1 by Kyrtsos and Huang (2002) discloses a monitoring method and system mounted onboard a vehicle which determines axle misalignment and tire wear while the vehicle is driven. Axle misalignment is determined by monitoring the lateral acceleration values on an axle over a certain amount of time, such as the distance traveled over a long trip, and monitoring the vertical acceleration values which are proportional to the ratio of the weight on each axle. Then calculating and comparing one axle's data to the other, a prediction of the amount of axle misalignment and tire wear can be made. Concluding that the final ratio calculated determines that one axle is more misaligned than the other. However, this system determines axle misalignment over a traveled period of time, delaying important alignment information which allows the continuation of premature tire wear, and further delays vehicle operating efficiency while waiting on final calculations.